docs: def arrays_to_string(file_prefix=None):
      """Returns registry for serialising arrays as a Base64 string."""
      return Registry(
          types={
              numpy.ndarray: SerNumpyArray(),
              numpy.floating: SerNumpyScalar()
          },
          hooks={
              '<ufunc>': SerUFunc()
          },
          hook_fn=_numpy_hook
      )